zero-digital-mutting transistor

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#21
I wouldn't like to say with regard to just copying another player and without seeing all the component values etc. All the little details come together.

This player is obviously designed (and the gain and response of the stages calculated and correctly configured) to work correctly. If that transistor is normally off under all the conditions that you use the player in then you can remove the transistor.

That has to be the first thing to measure before you alter anything. See if the transistor would conduct under your normal usage. If you remove the transistor then there is a slight influence of that 1800pf cap in combination with the 1k +22uf +47k series chain. The effect is extremely small (negligable probably).

If the transistor conducts under any of your usage conditions such as DVD playback, CD playback etc then you should refit them.
 
#22
Mooly said:
I wouldn't like to say with regard to just copying another player and without seeing all the component values etc. All the little details come together.

This player is obviously designed (and the gain and response of the stages calculated and correctly configured) to work correctly. If that transistor is normally off under all the conditions that you use the player in then you can remove the transistor.

That has to be the first thing to measure before you alter anything. See if the transistor would conduct under your normal usage. If you remove the transistor then there is a slight influence of that 1800pf cap in combination with the 1k +22uf +47k series chain. The effect is extremely small (negligable probably).

If the transistor conducts under any of your usage conditions such as DVD playback, CD playback etc then you should refit them.
Click to expand...
First thing thanks for the help bro 🙂

The 2900 works perfectly finished mod yesterday as well as I changed the OP AMP NJM2068 - I / V
to LM4562
I now only remains to decide which OP AMP to place
BA15218

(This audio circuit diagram of 3910)
 

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#23
Thats similar in concept but with very different values. Gain of that stage is 2 and the feedback return is DC coupled.

For the unit you are working on you need to measure the base/emitter voltage across the corresponding points where the transistor was fitted (and that you have now removed). If there is B-E voltage present in playback then it means the transistor was on (conducting) and so should be in place (or a link fitted)... ut then you loose the function of what happens when its supposed to be off. Its there for a reason and whether you remove it or short it out means you loose that function.
 
#24
Mooly said:
Thats similar in concept but with very different values. Gain of that stage is 2 and the feedback return is DC coupled.

For the unit you are working on you need to measure the base/emitter voltage across the corresponding points where the transistor was fitted (and that you have now removed). If there is B-E voltage present in playback then it means the transistor was on (conducting) and so should be in place (or a link fitted)... ut then you loose the function of what happens when its supposed to be off. Its there for a reason and whether you remove it or short it out means you loose that function.
Click to expand...

Thanks bro
The decision to remove this transistor made
After reading a lot of people did on the 2900 Mod.
So after removing it sounds A lot better
I was just curious about resistors 🙂
After your reply
I got the answer I wanted 🙂
Thank you.
If you could ask one more question
Now I installed the audio circuit on I / V amplifier LM4562
And buffer AD826
To what OP AMP would you recommend switching from BA15218
 
#26
Mooly said:
The 4562 is as good as anything for most situations. When swapping opamps you need to be aware of stability problems that might arise although there shouldn't be any problems with this. Not sure if you've seen this or not,

http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
Click to expand...
Yes no problem
It works fine circuit
No problems of
op amp oscillation 🙂
I researched a lot before all decision on replacing of each OP AMP.
I read your thread now.
Topic of the OP AMP fascinates me



These projects refreshing the electronics studies I learned a few years ago 🙂
(Although at the time it was mostly mathematics
And a electrical equation )
 
#27
Hello

Today i make the order to all the other parts of the finsh project
Its left only one thing to decide



After I changed in the circuit of 2900 The OP AMP

(I/V) NJM2068 to LM4562
(buffer) OP275 to AD826


Is left to replaced the filter OP AMP's - BA15218F
IC218
IC219
Like all good battle
There are two candidates in the arena 😉
OPA1662 VS LM6172

Who Will Win ?
 

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#31
Thanks I'll buy it
And I'll see how it affects the circuit 😉
I have some tests done
when All the parts arrive.
1) Comparison between the 10UF output capacitor
VISHAY MKT1813 vs VISHAY MKP735

2) Comparison of carbon resistors which have in the device to resistors VISHAY DALE 1%
3) See how much difference will replace the capacitors of the OP AMP
0.1 UF ceramic
I ordered the film capacitors VISHAY MKP1837- 0.1UF


I just hope that the OP AMP
OPA1662
Fit as a substitute of what was original BA15218 :soapbox:
 
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